Firstly it looks like a great hack so thank you for sharing with the community!
As you know digichat has 2 kind of installation: You can install it to your server and you can use their server. I wonder if your hack supports the chat rooms that are hosted in digichat servers too?
Also as far as I can see, the hack assumes you don't already have any user profile fields while creating hack profile fields but what if you already have some? Is it possible to rename hack fields "field1" "field2" etc.?
And a small typo in chatconfig.php: 'englisch.lang' is I guess 'english.lang'
:-)